Attenuation devices for smoothing of pressure surges in fluid systems and for reducing the resulting vibrations and noise can be divided mainly into two known groups of attenuation devices. One group includes hydropneumatic attenuators as hydraulic accumulators containing an additional gas volume. The other group includes fluid sound attenuators, so-called silencers, in which without an additional gas volume an attenuation effect takes place by reflection or absorption. Reference is made to the technical book “The Hydraulic Trainer, Volume 3,” published by Mannesmann Rexroth, pages 106 and 107, for the corresponding prior art.
With hydropneumatic attenuators good properties can be achieved in a frequency band extending from very low frequencies to about 400 Hz. These attenuators would then be suitable for use in fluid systems in which pressure pulsations occur in this frequency band due to operation of hydraulic pumps, their engagement and disengagement processes, and valve operating processes. Since these attenuators with additional gas volumes are both bulky and heavy, these attenuation devices cannot be used in many applications where there is very limited installation space and a lightweight construction is necessary, as is the case, for example, in hydraulic systems in motor vehicles. Other disadvantages of attenuation devices with gas filling are that their attenuation action varies depending on the temperature and that the attenuation action overall is degraded by gas losses due to permeation.
Conversely, so-called silencers are a far more compact and have a lightweight construction. However, their use is limited by the attenuation action being sufficient only at higher frequencies of more than about 200 Hz. This limitation prevents use in automotive engineering where in hydraulic systems assigned to the steering, braking and stability control systems or in active suspension systems, operating processes can take place in a very wide frequency band extending from very low frequencies to high frequencies of 500 Hz or more.
To solve these problems, DE 43 38 912 C1 discloses a pressure surge attenuator for reducing hydraulic shocks in fluid lines. In this known solution, the pressure fluctuations coupled to the compressive gas volume acting as a resilient attenuation element in hydropneumatically operating attenuators are coupled to a resilient material. This arrangement yields a frequency behavior similar to the hydropneumatic attenuators, at a conversely reduced size and reduced weight. However, an adequate attenuation action cannot be achieved by this known solution.